The Environmental Protection Agency (EPA) requires vehicle manufacturers to install on-board diagnostics (OBD) for emission control on their light-duty automobiles and trucks beginning with model year 1996. OBD systems (e.g., computer, microcontrollers, and sensors) monitor the vehicle's emission control systems to detect any malfunction or deterioration that causes emissions to exceed EPA-mandated thresholds. Such a system, for example, includes an oxygen sensor located in the vehicle's exhaust manifold and tailpipe.
The EPA requires that information monitored or calculated by OBD systems is made available through a standardized, serial 16-pin connector referred to as the DLC (Diagnostic Link Connector) or OBD connector. All physical and electrical characteristics of this connector are standard for all compliant vehicles sold in the United States after 1996. The EPA also mandates that, when emission thresholds are exceeded, diagnostic information characterized by OBD systems must be stored in the vehicle's computers so that it can be used during diagnosis and repair.
A second generation of OBD systems (“OBD-II” systems) monitors a wider range of data than the original OBD systems. The data monitored includes emission information, performance data, faults, and the like. The data can then be analyzed and/or employed to diagnose operation of a host vehicle. As an example, the monitored data can be analyzed to infer the vehicle's emission performance. In addition to emissions, OBD-II systems monitor vehicle speed, engine temperature, and intake manifold pressure. OBD-II systems also query and set manufacturer-specific data, such as data relating to the vehicle's engine, transmission, brakes, alarm, entertainment systems. OBD-II systems also monitor emission performance setting diagnostic trouble codes (DTCs), which indicate a mechanical or electrical problem with the vehicle. DTCs typically result in lighting a vehicle's MIL (Malfunction Indicator Lamp), which provides a visual notice to an operator and/or service technician.
In addition to the OBD-II systems, most vehicles manufactured after 1996 have electronic control units (ECUs) that control internal electromechanical actuators. Examples include ECUs that control fuel-injector pulses, spark-plug timing, and anti-lock braking systems. Generally, ECUs transmit status and diagnostic information over a shared, standardized electronic bus in the vehicle. The bus effectively functions as an on-board computer network with many processors, each of which transmits and receives data. The primary computers in this network are the vehicle's engine control module (ECM) power train control module (PCM), and transmission control module (TCM). The PCM typically controls or monitors ECUs associated with the vehicle's power train (e.g., its engine, transmission, and transfer case).
When a vehicle is serviced, data from the standardized bus can be queried using external diagnostic equipment, for example scan tools, that connect to the above-described 16-pin electrical connector (called an OBD-II connector for vehicles made after 1996). The OBD-II connector is typically located under the vehicle's dashboard on the driver's side. Data transferred through the connector to the scan tool yields data that identify a status of the vehicle and whether or not a specific component of the vehicle has malfunctioned. This facilitates the service process.
On board vehicle diagnostic systems, such as the OBD and OBD-II systems, are able to communicate via one or more protocols. Typically, vehicle information tools are also able to communicate via one or more protocols. The vehicle information tools and the vehicle diagnostic systems can then communicate with each other so long as they share one or more common protocols. Unfortunately, protocols continue to be developed that are employable by vehicle diagnostic systems and/or vehicle information tools. As a result, it can occur that a common protocol between a given vehicle information system and a given scan tool does not exist. As one example, a vehicle diagnostic system communicates via a newer protocol that an older vehicle information tool does not employ. As a result, the vehicle information system and the older scan tool are unable to communicate. As another example, a vehicle information system may communicate via an older protocol that a more recent scan tool does not employ. Once again, as a result, the vehicle information system and the scan tool are unable to communicate.